Drupal blocks
One of the key ways of customizing Gutenberg is the ability to embed Drupal blocks as Gutenberg blocks. In Drupal, almost everything on the site gets rendered inside of a block, which means practically anything on the site is accessible from inside Gutenberg.
This includes things like the breadcrumb,
forms,
or even views:
Enabling Drupal blocks
Not every block is available in Gutenberg by default. Like Gutenberg itself, Drupal blocks are exposed to Gutenberg on a per-content-type basis. To do this, edit the content type of your choice, then click on the "Gutenberg Experience" vertical tab at the bottom of the page. You will see an accordion labelled "Allowed Drupal Blocks". Select all the Drupal blocks you want available in Gutenberg then you can save the content type.
You should now see a list of Drupal blocks available in the Gutenberg block browser:
In part 5 of this series, we will examine how to create custom, reusable groups of Gutenberg blocks called patterns.